1. Field of the Invention
The present invention relates to a flexible disk device for use in an external memory device, etc., of an electronic computer, and more specifically to a driving mechanism for driving a carriage.
2. Description of the Prior Art
Referring to FIG. 7, there is illustrated a conventional flexible disk device in a perspective view which includes a read/write head positioning mechanism with use of a lead screw and a pulse motor, as disclosed in "Magnetic Recording Current Technology, and Apparatuses and Instruments therefor" published by Sogo Gijutsu Shuppan, 1984. In the same figure, designated at 1 is a carriage, 2 is a pulse motor, 3 is a lead screw, 4a is a guide rod, 5 is a read/write head, 6 is a flexible disk cartridge, 7 is a base, 8 is an electric circuit board, 9 is a spindle motor, 11 is a rotary/straight movement conversion mechanism, 51 is a head arm, and 61 is a magnetic disk. Additionally, FIG. 8 is a sectional view illustrating a prior 5.25 inch flexible disk device using a linear pulse motor for a read/write head positioning mechanism, as disclosed in Nikkei Mechanical No. 1986. 9. 22. In the same figure, designated at 2a is a linear pulse motor, 4a is a guide rod, (6a) is a 5.25 inch diskette, and (61a) is a magnetic disk. The like or equivalent portions as those shown in FIG. 7 are designated by like symbols.
Operation of the conventional device is as follows.
In order to move the read/write head which is to move in contact with the upper and lower surfaces of the magnetic disk 61 mounted on the spindle motor 9, in an example illustrated in FIG. 7, for example, a general rotative pulse motor 2 is used to turn the lead screw 3 coupled to a rotor thereof and convert the rotation of the lead screw 3 through the rotary/straight movement conversion mechanism 11, whereby the carriage 1 is moved. Additionally in an example illustrated in FIG. 8, the carriage 1 directly coupled to a rotor of a linear pulse motor 2a undergoes step movement corresponding to applied pulse voltage to position the read/write head coupled to the carriage 1 through the arm 51.
The conventional flexible disk device is constructed as described above. Accordingly, when it is intended to perform information access with larger capacity and at a higher speed compared with the present situation, a pulse motor has a structural limitation due to the restriction of a mechanical machining size to the amount of a minimum step fed by one pulse to prevent the density of a recorded track from being increased. Additionally, such a pulse motor suffers from detuning as the rotor is speeded up and hence fails to track a high speed head movement.